• Geomechanics and Engineering
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• 제13권4호
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• pp.601-619
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• 2017

Cantilever retaining wall movements generally depend on the intensity and duration of ground motion, the response of the soil underlying the wall, the response of the backfill, the structural rigidity, and soil-structure interaction (SSI). This paper investigates the effect of material properties on seismic response of backfill-cantilever retaining wall-soil/foundation interaction system considering SSI. The material properties varied include the modulus of elasticity, Poisson's ratio, and mass density of the wall material. A series of nonlinear time history analyses with variation of material properties of the cantilever retaining wall are carried out by using the suggested finite element model (FEM). The backfill and foundation soil are modelled as an elastoplastic medium obeying the Drucker-Prager yield criterion, and the backfill-wall interface behavior is taken into consideration by using interface elements between the wall and soil to allow for de-bonding. The viscous boundary model is used in three dimensions to consider radiational effect of the seismic waves through the soil medium. In the seismic analyses, North-South component of the ground motion recorded during August 17, 1999 Kocaeli Earthquake in Yarimca station is used. Dynamic equations of motions are solved by using Newmark's direct step-by-step integration method. The response quantities incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that while the modulus of elasticity has a considerable effect on seismic behavior of cantilever retaining wall, the Poisson's ratio and mass density of the wall material have negligible effects on seismic response.

• 한국태양에너지학회 논문집
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• 제23권1호
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• pp.1-8
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• 2003

Various efforts to combine new high-tech materials with solar system have been progressed nowadays in order to improve the performance of the existing passive solar system. TIM(Transparent Insulation Material) replacing the conventional outer building envelope glazing as well as the wall is good example for this trend. TI integrated wall is a thermal mass wall with a special shaped TIM instead of using typical envelope materials The tested TIM type is a small(diameter 4mm and thickness 50mm) capillary tube of Okalux model and cement brick(density 1500kg/m3). The purpose of this study was to analyze the thermal performance through the actual measurements performed in a test cell. This study was carried out to justify the following issues. 1) the impact of Tl-wall over the temperature variations 2) the impact of mass wall surface absorptance over the transient thermal behavior and 3) the impact of thermal mass wall thickness over the temperature variations. Finally, as results indicated that the peak time of room temperature was shifted about one hour early when absorptance of thermal mass wall changed from 60% to 95% for the 190mm thickness thermal mass wall test case. the temperature difference of both surfaces of thermal mass wall surface showed about $23^{\circ}C$ during a day of March for the 380mm thickness thermal mass wall case. However, the thermal mass wall was over-heated by outside temperature and solar radiation in a day of May the temperature difference of both surfaces of thermal mass wall surface was indicated $10^{\circ}C$ and inside temperature was observed more than average 22C.

• 한국지반환경공학회 논문집
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• 제19권2호
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• pp.13-21
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• 2018

The magnitude and distribution of earth pressure on the excavation wall in jointed rock mass were examined by considering different wall permeability conditions as well as rock types and joint inclination angles. The study was numerically extended based on a physical model test (Son & Park, 2014), considering rock-structure interactions with the discrete element method, which can consider various characteristics of rock joints. This study focused on the effect of the permeability condition of excavation wall on the earth pressure in jointed rock masses under a groundwater condition, which is important but has not been studied previously. The study results showed that the earth pressure was highly influenced by wall permeability as well as rock type and joint condition. Earth pressure resulted from the study was also compared with Peck's earth pressure in soil ground, and the comparison clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground.

• 한국전산유체공학회지
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• 제17권2호
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• pp.42-52
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• 2012

Direct Numerical Simulation(DNS) of turbulent mass transfer in fully developed turbulent pipe flow has been performed to study the effect of wall boundary conditions on the concentration fields at $Re_{\tau}$=180 based on friction velocity and pipe radius. Fully developed turbulent pipe flows for Sc=0.71 are studied with two different wall boundary conditions, namely, constant mass flux and constant wall concentration. The mean concentration profiles and turbulent mass fluxes obtained from the present DNS are in good agreement with the previous numerical results currently available. To investigate the effects of wall boundary condition on the turbulent mass transfer, the mean concentration profile, root-mean-square of concentration fluctuation, turbulent mass fluxes and higher-order statistics(Skewness and Flatness factor) are compared for the two cases. Furthermore, the budgets of turbulent mass fluxes and concentration variance were computed and analyzed to elucidate the effects of wall boundary conditions on the turbulent mass transfer.

• 수산해양기술연구
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• 제47권1호
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• pp.46-58
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• 2011

A steady-state analysis and a simple dynamic model as simplified methods are developed, and results of energy consumption loads are compared with results obtained using computer to evaluate the analytical solution. Before obtaining simplified model a mathematical model is formulated for the effect of wall mass on the thermal performance of four different houses having various wall construction. This analytical study was motivated by the experimental work of Burch et al. An analytical solution of one-dimensional, linear, partial differential equation for wall temperature profiles and room air temperatures is obtained using the Laplace transform method. Typical Meteorological Year data are processed to yield hourly average monthly values. This study is conducted using weather data from four different locations in the United States: Albuquerque, New mexico; Miami, Florida; Santa Maria, California; and Washington D.C. for both winter and summer conditions. The steady state analysis that does not include the effect of thermal mass can provide an accurate estimate of energy consumption in most cases except for houses #2 and #4 in mild weather areas. This result shows that there is an effect of mass on the thermal performance of heavily constructed house in mild weather conditions. The simple dynamic model is applicable for high cycling rates and accurate values of inside wall temperature and ambient air temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.22-29
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• 2001

The present study investigates the effects of various rib arrangements and rotating on heat/mass transfer in the cooling passage of gas turbine blades. The cooling passage has very complex flow structure, because of the rib turbulator and rotating effect. Experiments and numerical calculation are conducted to investigate the complex flow structures and heat transfer characteristics; the numerical computation is performed using a commercial code, FLUENT ver.5, to calculate the flow structures and the experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. For the rotating duct tests, the test duct, which is the cross section of is $20mm\times40mm$ (the hydraulic diameter, $D_h$, of 26.7 mm, has two-pass with $180^{\circ}$ turning and the rectangular ribs on the wall. The rib angle of attack is $70^{\circ}$ and the maximum radius of rotation is $21.63D_h$. The partition wall has 10 mm thickness, which is 0.5 times to the channel width, and the distance between the tip of the partition wall and the outer wall of the turning region is 26.7 mm $(1D_h)$. The turning effect of duct flow makes the very complex flow structure including Dean type vortex and high turbulence, so that the heat/mass transfer increases in the turning region and at the entrance of the second pass. The Coriolis effect deflects the flow to the trailing surface, resulting in enhancement of the heat/mass transfer on the trailing surface and reduction on the leading surface in the first pass. However, the opposite phenomena are observed in the second pass. The each rib arrangement makes different secondary flow patterns. The complex heat/mass transfer characteristics are observed by the combined effects of the rib arrangements, duct rotation and flow turning.

• 한국화재소방학회논문지
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• 제18권4호
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• pp.27-34
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• 2004

CO₂소화장치의 CO₂노즐과 방호공간 내 벽 사이의 거리변화에 따른 유동 및 CO₂질량전달효과를 분석하기 위하여 CO₂노즐과 후측 벽 사이의 거리를 변화시키면서 전산모이실험을 3차원 비정상상태로 수행하였다. 유동장과 CO₂소화제 농도장을 계산하였다. CO₂노즐과 후측 벽 사이의 거리 증가에 따라 다른 재 순환 유동형태와 벽면제트기류가 형성되었다. CO₂ 소화제 질량전달은 모든 경우에서 각 벽으로부터 방호공간의 중앙으로 일어나지만 CO₂소화제 노즐의 전 후 영역의 CO₂질량분율은 CO₂노즐과 벽 사이의 거리 증가에 따라 높거나 낮게 나타났다.

• 한국지반환경공학회 논문집
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• 제18권9호
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• pp.5-9
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• 2017

일반적인 지하수에 대해서는 지반공학적 방법((1)지반을 굴착한 후 지중연속벽체의 육안 확인, (2)벽체의 코아 채취 후 일축압축강도시험, (3)벽체 코아 채취 시 현장 투수시험)으로 주열식 지중연속벽체의 차수효과를 확인할 수 있다. 그러나, 폐기물 매립장내에서 발생하는 침출수와 같은 고농도 오염수 유출이나 침투의 차단에 대해서는 주변 지하수 등을 대상으로 현장에서 pH, 수온, 염분 농도 등을 측정하고 이들의 성분시험을 실시하여 기본 성분 및 성분비 등의 특성을 분석한 후 일치성 유사성을 판정하며, GC-MS를 이용하여서는 이들 시료수의 크로마토그램에 대한 피크의 높고 낮음의 차이 등 전반적인 분포패턴을 비교하여 간편하게 유사성 판정을 추가적으로 실시함으로써 객관성 있게 주열식 지중연속벽체의 차수효과를 확인하여야 한다.

• 한국지반환경공학회 논문집
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• 제19권10호
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• pp.27-34
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• 2018

원호활동파괴가 발생한 해안 폐기물 매립장에서 기초지반 전단강도의 보완과 폐기물 침출수가 지하수나 인접지반으로 유동되는 것을 차단하는 최종 시설로서 시멘트계 지중벽체를 시공한 후, 침출수 차단효과를 확인하였다. (1) 육안 확인 및 (2) 압축강도 시험에 의하면 지중에 시공된 벽체의 품질이 상당히 양호하다는 사실을 확인할 수 있고 (3) 현장 투수시험과 (4) 성분 및 성분비 분석과 (5) 질량 분석기를 통해서 얻게 되는 크로마토그램의 분포패턴 판정 등 중복적인 실험 및 조사 분석에 의해서 벽체의 수밀성이나 침출수의 이동에 대한 차단성이 매우 크다는 것을 확인할 수 있었다. 따라서, 폐기물 매립장 내에서 발생하는 침출수와 같은 고농도 환경오염수가 매립장 밖으로 유출되거나 침투하는 것에 대한 신뢰적인 차단 여부는 이 5가지의 조사 및 시험을 실시하는 방안에 의하여 객관적으로 판단될 수 있다고 사료된다.

• 한국전산유체공학회지
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• 제17권3호
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• pp.59-67
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• 2012

Large Eddy Simulation(LES) of turbulent mass transfer in fully developed turbulent pipe flow has been performed to study the effect of Reynolds number on the concentration fields at $Re_{\tau}=180$, 395, 590 based on friction velocity and pipe radius. Dynamic subgrid-scale models for the turbulent subgrid-scale stresses and mass fluxes were employed to close the governing equations. Fully developed turbulent pipe flows with constant mass flux imposed at the wall are studied for Sc=0.71. The mean concentration profiles and turbulent intensities obtained from the present LES are in good agreement with the previous numerical and experimental results currently available. The effects of Reynolds number on the turbulent mass transfer are identified in the higher-order statistics(Skewness and Flatness factor) and instantaneous concentration fields. The budgets of turbulent mass fluxes and concentration variance were computed and analyzed to elucidate the effect of Reynolds number on turbulent mass transfer. Furthermore, to understand the correlation between near-wall turbulence structure and concentration fluctuation, we present an octant analysis in the vicinity of the pipe wall.